Chapter 5: The Integumentary System. What are the structures and functions of the integumentary system?

Transcription

1 Chapter 5: The Integumentary System What are the structures and functions of the integumentary system? 1

2 Size of the Integument The integument is the largest system of the body: 16% of body weight 1.5 to 2 m 2 in area 1. cutaneous membrane (skin) 2. accessory structures Parts of the Integumentary System Figure 5 1 2

3 Parts of the Cutaneous Membrane Outer epidermis: superficial epithelium (epithelial tissues) Inner dermis: connective tissues Accessory Structures Originate in the dermis Extend through the epidermis to skin surface: 3

4 The Subcutaneous Layer Subcutaneous layer (superficial fascia or hypodermis): loose connective tissue below the dermis location of hypodermic injections Functions of Skin Protects underlying tissues and organs Excretes salts, water, and organic wastes (glands) Maintains body temperature (insulation and evaporation) 4

5 Functions of Skin Synthesizes vitamin D 3 Stores lipids Detects touch, pressure, pain, and temperature What are the main structures and functions of the epidermis? 5

6 Organization of the Epidermis Figure 5 2 Thin Skin v. Thick Skin 6

7 Structures of the Epidermis The 5 strata of keratinocytes in thick skin Figure 5 3 Layers of the Epidermis From basal lamina to free surface: stratum germinativum stratum spinosum stratum granulosum stratum lucidum stratum corneum 7

8 Stratum Germinativum The germinative layer : has many germinative (stem) cells or basal cells is attached to basal lamina by hemidesmosomes forms a strong bond between epidermis and dermis Structures of Stratum Germinativum Epidermal ridges (e.g., fingerprints) Dermal papillae (tiny mounds): increase the area of basal lamina strengthen attachment between epidermis and dermis 8

9 Ridges and Ducts Figure 5 4 Cells of Stratum Germinativum Merkel cells: found in hairless skin respond to touch (trigger nervous system) Melanocytes: contain the pigment melanin scattered throughout stratum germinativum 9

10 Stratum Spinosum The spiny layer : produced by division of stratum germinosum 8 10 layers of keratinocytes bound by desmosomes cells shrink until cytoskeletons stick out (spiny) Cells of Stratum Spinosum Continue to divide, increasing thickness of epithelium Contain Langerhans cells, active in immune response 10

11 Stratum Granulosum The grainy layer Stops dividing, starts producing: keratin: a tough, fibrous protein makes up hair and nails The clear layer : Stratum Lucidum found only in thick skin covers stratum granulosum 11

12 The horn layer : Stratum Corneum exposed surface of skin 15 to 30 layers of keratinized cells water resistant shed and replaced every 2 weeks Keratinization The formation of a layer of dead, protective cells filled with keratin Occurs on all exposed skin surfaces except eyes 12

13 Skin Life Cycle It takes days for a cell to move from stratum germinosum to stratum corneum Perspiration Insensible perspiration: interstitial fluid lost by evaporation through the stratum corneum Sensible perspiration: water excreted by sweat glands 13

14 Water Loss Through Skin Dehydration results: from damage to stratum corneum, e.g., burns and blisters (insensible perspiration) from immersion in hypertonic solution, e.g., seawater (osmosis) Water Gain Through Skin Hydration: results from immersion in hypotonic solution, e.g., freshwater (osmosis) causes stretching and wrinkling skin 14

15 Skin Color Skin color depends on: the pigments carotene and melanin blood circulation (red cells) Function of Melanocytes Melanin protects skin from sun damage Ultraviolet (UV) radiation: causes DNA mutations and burns which lead to cancer and wrinkles 15

16 Melanocytes Figure 5 5 Illness and Skin Color Jaundice: buildup of bile produced by liver yellow color Addison s disease: and other diseases of pituitary gland skin darkening Vitiglio: loss of melanocytes loss of color 16

17 Vitamin D Epidermal cells produce cholecalciferol (vitamin D 3 ): in the presence of UV radiation Liver and kidneys convert vitamin D into calcitriol: to aid absorption of calcium and phosphorus Deficiency: rickets The epidermis: KEY CONCEPT is a multilayered, flexible, self-repairing barrier prevents fluid loss protects from UV radiation produces vitamin D 3 resists abrasion, chemicals, and pathogens 17

18 What are the structures and functions of the dermis? The Dermis Is located between epidermis and subcutaneous layer Anchors epidermal accessory structures (hair follicles, sweat glands) Has 2 components: outer papillary layer deep reticular layer 18

19 The Papillary Layer Consists of areolar tissue Contains smaller capillaries, lymphatics, and sensory neurons Has dermal papillae projecting between epidermal ridges The Reticular Layer Consists of dense irregular connective tissue Contains larger blood vessels, lymph vessels, and nerve fibers Contains collagen and elastic fibers Contains connective tissue proper 19

20 Lines of Cleavage Collagen and elastic fibers in the dermis: are arranged in parallel bundles resist force in a specific direction Lines of cleavage establish important patterns: a parallel cut remains shut, heals well a cut across (right angle) pulls open and scars Dermal Circulation Figure

21 The dermis: KEY CONCEPT provides mechanical strength, flexibility and protection is highly vascularized contains many types of sensory receptors What are the structures and functions of the subcutaneous layer? 21

22 The Hypodermis The subcutaneous layer or hypodermis: lies below the integument stabilizes the skin allows separate movement made of elastic areolar and adipose tissues connected to the reticular layer of integument by connective tissue fibers What determines hair growth, texture, and color? 22

23 Location of Hair The human body is covered with hair, except: palms soles lips portions of external genitalia Functions of Hair Protects and insulates Guards openings against particles and insects Is sensitive to very light touch 23

24 The Hair Follicle Is located deep in dermis Produces nonliving hairs Is wrapped in a dense connective-tissue sheath Base is surrounded by sensory nerves (root hair plexus) Structures of Hair and Follicles Figure 5 9a 24

25 Accessory Structures of Hair Arrector pili: involuntary smooth muscle causes hairs to stand up produces goose bumps Sebaceous glands: lubricate the hair control bacteria Hair root: Regions of the Hair lower part of the hair attached to the integument Hair shaft: upper part of the hair not attached to the integument 25

26 Inside the Follicle Figure 5 9b How Hair Grows Hair begins deep in the dermis: the hair papilla contains capillaries and nerves the hair bulb produces hair matrix 26

27 Medulla: the central core Cortex: the middle layer Cuticle the surface layer Layers in a Hair Structure of a Hair Figure 5 9d 27

28 Layers in the Follicle Internal root sheath: the inner layer contacts the cuticle in lower hair root External root sheath: extends from skin surface to hair matrix Glassy membrane: a dense connective-tissue sheath contacts connective tissues of dermis Structures of a Follicle Figure 5 9c 28

29 Types of Hairs Vellus hairs: soft, fine cover body surface Terminal hairs: heavy, pigmented head and eyebrows other parts of body after puberty Hair color Produced by melanocytes at the hair papilla Determined by genes What are the skin glands and secretions? 29

30 Exocrine Glands Sebaceous glands (oil glands): holocrine glands secrete sebum Sweat glands: merocrine glands watery secretions Sebaceous Glands Figure

31 Sebum Contains lipids and other ingredients Lubricates and protects the epidermis Inhibits bacteria What are the functions of sweat glands? 31

32 Apocrine: Types of Sweat Glands found in armpits, around nipples, and groin Merocrine: widely distributed on body surface especially on palms and soles Apocrine Sweat Gland Figure 5 11a 32

33 Apocrine Sweat Glands Associated with hair follicles Produce sticky, cloudy secretions Break down and cause odors Merocrine Sweat Glands Also called eccrine glands: coiled, tubular glands discharge directly onto skin surface sensible perspiration water, salts, and organic compounds 33

34 Merocrine Sweat Gland Figure 5 11b Functions of Merocrine Sweat Cools skin Excretes water and electrolytes Flushes microorganisms and harmful chemicals from skin 34

35 Other Integumentary Glands Mammary glands: produce milk Ceruminous glands: protect the eardrum produce cerumen (earwax) Control of Glands Autonomic nervous system: controls sebaceous and apocrine sweat glands works simultaneously over entire body Merocrine sweat glands: are controlled independently sweating occurs locally Thermoregulation 35

36 What is the structure of nails, and how do they grow? Structure of a Nail Figure

37 Nail body: Structures of Nails the visible portion of the nail covers the nail bed Lunula: the pale crescent at the base of the nail Nail root: Produces growth Sides of nails: Structures of Nails lie in lateral nail grooves surrounded by lateral nail folds Skin beneath the free edge of the nail: is the hyponychium Visible nail emerges: from the eponychium (cuticle) at the tip of the proximal nail fold 37

38 How does injured skin respond and repair itself? Repair of Localized Injuries to the Skin: Step 1 Bleeding occurs Mast cells trigger inflammatory response Figure 5 13 (Step 1) 38

39 Repair of Localized Injuries to the Skin: Step 2 A scab stabilizes and protects the area Figure 5 13 (Step 2) The Inflammatory Response Germinative cells migrate around the wound Macrophages clean the area Fibroblasts and endothelial cells move in, producing granulation tissue 39

40 Repair of Localized Injuries to the Skin: Step 3 Fibroblasts produce scar tissue Inflammation decreases, clot disintegrates Figure 5 13 (Step 3) Repair of Localized Injuries to the Skin: Step 4 Fibroblasts strengthen scar tissue A raised keloid forms Figure 5 13 (Step 4) 40

41 Effects of Aging Epidermal thinning Decreased numbers of Langerhans cells Decreased vitamin D 3 production Decreased melanocyte activity Decreased glandular activity (sweat and oil glands) Reduced blood supply Decreased function of hair follicles Reduction of elastic fibers Decreased hormone levels Slower repair rate SUMMARY (1 of 4) Division of: integument into epidermis and dermis epidermis into thin skin and thick skin Layers of the epidermis: stratum germinosum stratum spinosum stratum lucidum stratum corneum 41

42 SUMMARY (2 of 4) Roles of epidermal ridges and dermal papilla Functions of specialized cells: Langerhans cells Merkel cells Skin pigments: carotene Melanin Metabolic functions of epidermis: vitamin D 3 epidermal growth factor SUMMARY (3 of 4) Divisions of the dermis: papillary layer reticular layer Mobility of the dermis: stretch marks lines of cleavage Role of the subcutaneous layer 42

43 SUMMARY (4 of 4) Structure of hair and hair follicles Glands of the skin: sebaceous sweat Ceruminous Structure of nails Processes of inflammation and regeneration Effects of aging on the integument 43